Container and method of making the same



fi 1944- J. G. MARK ETAL CONTAINER AND METHOD MAKING THE SAME Filed July 27, 1940 v Enventors: tki'ob GTMark, and .FT-ancis T K'Lanzyaw (Ittbmeg Patented Feb. 15, 1944 CONTAINER AND METHOD OF MAKING THE SAME Jacob G. Mark, Brookline, and Francis W. Lanigan, Belmont, Mass, assignors to Dewey and Almy Chemical Company, North Cambridge, Mass., a corporation of Massachusetts Application July 27, 1940, Serial No. 347,984 In Great Britain August 15, 1939 11 Claims.

The present invention relates to containers and more particularly to the sealing of wrappings and cartons of paper or similar material.

It has become customary in the use of paper for the wrapping of articles such as bread, and in the use of paper board for the manufacture of cartons intended for the packaging of foodstufis, fruit drinks and the like, to provide the material with a coating of a wax or a wax-containing composition for the purpose of preserving the taste or flavour of the contents of the wrapping, carton or the like or to prevent the ingress to the contents of air and moisture. However, the sealing of such wrappings or containers has presented some diificulty.

One known method has been to apply heat to the surfaces to be sealed, for example, the flaps in the case of a carton, or the edges of the wrapper in the case of a bread or other wrapper, whereby the wax is temporarily softened and a wax-to-wax bond is formed. While such a bond is quite satisfactory for the purpose of preventing the entry of air and moisture into the wrapping or container, it is usually inadequate to withstand the handling which cartons, boxes and wrap pings receive from the retail shop keeper and the purchaser. In order to obtain a stronger bond, it has been proposed to seal the containers or wrappings by means of the usual paper adhesives, such as glue. This method, however, entails an additional step consisting in blanking out the sealing surfaces prior to the application of wax to the paper or paper board, thereby increasing both the time and cost of production.

It is an object of this invention to provide an improved seal for containers, such as cartons, or wrappings, coated with a wax or a similar fusible air and moisture excluding composition, which obviates the foregoing disadvantages. A further object is to provide an improved seal for paper and paper board containers and wrappings which have a coating of a wax or a similar composition, the sealing means being such as to permit the use of conventional sealing apparatus hitherto em ployed for producing a wax-to-wax seal.

According to the present invention, the sealing surfaces of a container or wrapping coated with a wax or a similar composition are provided heneath the wax layer with a layer of an adhesive composition which will become tacky and adhesive when heated. For convenience this class of materials will be referred to herein as heatactivable adhesives.

The invention includes within its scope a process for the sealing of a carton or other container or wrapping in which the sealing surfaces are first provided with a layer of a heat-activable adhesive, then with a layer of a wax composition, or an equivalent fusible air and moisture excluding material, and are then temporarily subjected to a temperature suflicient to melt the wax layer and to render the heat-activable adhesive composition soft and plastic whereupon the sealing surfaces are firmly pressed together to complete the seal.

An illustrative embodiment of the invention is shown in the accompanying drawing, in which Figure 1 is a perspective view of a carton provided with adhesive layers on its flaps;

Figure 2 is a perspective View of the same carton after it has been provided with an over-all coating of wax; I

Figure 3 is a perspective view of the completed seal;

Figure 4 is a section on line 4-4 of Figure 3 showing the relation of the flap coatings before sealing, the thickness of the flaps being exaggerated for clearer illustration;

Figure 5 is a section similar to Figure 4 showing the seal completed; and

Figure 6 is a perspective view of a carton end illustrating a modified arrangement of the adhe-' sive layers.

In carrying the present invention into efiect according to one embodiment, a thermoplastic resin composition, for example, a solution of vinyl actate in a suitable solvent, such as ethylene dichloride, is applied to the flaps of a carton in any suitable fashion, whereupon the carton is dipped in a tank of molten paraffin wax and then allowed to drain. The wax coating completely covers the previously applied layer of resin composition. When it is desired to form the seal, the sealing surfaces are passed under conventional hot-plate sealing apparatus. Sufiicient heat is transmitted through the paper board not only to make the resin plastic and tacky; but to melt the wax coating which flows off the surface of the thermoplastic layer under pressure applied by the apparatus to the sealing surfaces, and collects around the edges Where the pressure is somewhat less. The vinyl acetate layers fuse together and form a seal, the strength of which is even beyond that of the paper itself, so that no strain less than one which would destroy the package is capable of rupturing the seal. Furthermore, since the wax which has melted from the sealing surfaces collects around the layer of adhesive, any possibility of air or moisture entering the container between the sealing surfaces is prevented.

While other solvents for the vinyl acetate may be employed, for example, ethyl or methyl alcohol, acetone, etc., it is preferred to employ ethylene dichloride since it is non-inflammable.

The invention is illustrated in Figures 1 and '2 as applied to a carton of cardboard or similar material. The carton is formed in the usual way by folding a died-out blank to form a rectangular carton body I provided at each end with flaps which may be interfolded and adhesively joined to provide an end closure for the carton. In Figure 1 the flaps at the end 2 have been folded together and sealed with a conventional adhesive such as glue. The sealing of this first end presents no difficulties because it may be sealed before the carton is provided with a wax coating. The small flaps 6 and 8 are provided with layers of heat-activable adhesive l2 and I3, respectively, on their upper surface. The second flap I is provided with layers of heat-activable adhesive l4 and IS on both of its faces. The outer flap 4 is provided with a layer of adhesive I8 on its inner face only. .These layers of adhesive may be applied to the flaps by brushing or spraying, or in any other suitable manner. It is preferred, however, for reasons of economy to apply the adhesive by roll coating as the blanks are being formed. In some cases the adhesive will be applied to both sides of all of the flaps by roll coating the stock while it is still in the form of a web. The slight additional cost of -the adhesive on the flap sides which need not have been coated is more than offset by the saving which this simplification of the coating procedure permits.

The carton may now be provided with an overall coating of a moisture and air excluding material such as ordinary paraffin wax or an equivalent. As illustrated in Figure 2, this coating 20 extends over the entire inside and outside surface of the carton, covering the previously applied adhesive layers. This coating may be applied in the conventional manner by flooding or dipping the carton and permitting it to drain in an inverted position.

After the carton has been filled, the flaps are interfolded and closed on conventional carton closing machinery. As the flaps are folded to-- gether each flap is separated from the adjacent one by at least one layer of adhesive which is covered with the wax. Thus in Figure 4 the outer flap 4. having its adhesive layer I8 covered with a wax coating 22, folds down upon the intermediate flap In having on its upper surface the adhesive layer I6 covered by a wax layer 24. As

the carton progresses through the closing and sealing machine the flaps are subjected to heat and pressure. Under the influence of the heat the wax layers 22 and 24 will become fluid and will be caused by the pressure to flow from between the flaps permitting the adjacent layers of adhesive to come into direct contact. These two layers will then fuse together forming an adhesive bond 26 (Figure uniting flaps 4 and Ill. The surplus wax from layers 22 and 24 collects at the sides of the flaps where it cools, forming additional seals such as 28 and 30 which further insure an effective sealing of the carton end. It will be understood that an adhesive bond between the small flaps 6 and 8 and the intermediate flap I0 is formed in a similar manner.

If preferred, the adhesive may be applied to parts only of the flaps. Thus, in Figure 6 the small flaps 5 and I are provided with narrow stripes of adhesive 9 and H along their margins adjacent the carton body. The intermediate flap 33 is provided with cooperating stripes of adhesive l5 and I! on the corresponding margins of its inner face. On its upper face the intermediate flap 33 is provided with a U-shaped stripe I! along three of its margins. The inside face of the upper flap 2| is provided with a stripe of adhesive 23 positioned to coincide with the stripe I9 on flap 33 when the outer flap 2| is folded down on the latter. This arrangement provides effective sealing of all of the flaps along their periphery. The quantity of adhesive used will be substantially less than that required in the modification illustrated in Figures 1' and ,2.

As the heat-activable adhesive any material which will become adhesive and tacky at a reasonably low temperature may be used. It is preferable that the melting point of the adhesive be higher than that of the protective coating under which it is applied. The synthetic resins of the thermoplastic type which meet the foregoing qualifications are particularly suitable. Among these may be mentioned the polyvinyl acetates, polyvinyl chlorides, the co-polymers formed by conjoint polymerization of vinyl chloride and vinyl acetate, the resins of the acrylic type re-- sulting from the polymerization of acrylic acid or its esters and derivatives or homologues thereof, and the polyvinyl acetals. Appropriate modifying agents, such as plasticizers, may be incorporated with the resins. Cellulose derivatives properly plasticized may also be used.

It is preferred that the heat-activable adhesive and the over-all protective coating material be substantially immiscible at the melting temperature of the latter, otherwise a too great dilution of the adhesive by the material of the protective coating may occur during the sealing of the carton, resulting in a weak or imperfect bond between the sealed parts. The best results are obtained when the adhesive material is such that the molten protective coating material readily flows over it under the sealing pressure. The thermoplastic synthetic resins satisfy these requirements very well when the protective coating is formed from a wax or a wax-rubber composition.

We claim:

1. The method of forming a container which comprises forming a container blank having a seam area adapted to be adhesively joined to another seam area of th blank to form a seam, applying to the seam area a heat-activable adhesive immiscible with wax, and then coating the blank and adhesive witha wax.

2. A wax coated carton comprising a carton body provided with a flap adapted to be folded together with other flaps on the body and adhesively united thereto to form a closure for the carton, the flap having on its surface a layer of heat-activable adhesive immiscible with wax and underlying the wax coating;

3. A container blank comprising a blank body having a seam area adapted to be united to another seam area in forming the blank into a container, a layer of a heat-activable adhesive on the surface of the body and within a seam area and a coating of fusible air and moisture excluding material immiscible with the adhesive covering the body and overlying the adhesive.

4. A sealed container having a seam formed by adjacent portions of the container body which lie in face-to-face relation, a heat-activable adhesive layer between the faces and forming an adhesive bond joining said portions together and an air and moisture excluding coating immiscible with the adhesive covering the inside and outside surfaces of the container body and surrounding the adhesive layer. i

5. The method of forming a carton which come prises forming a blank provided with flaps adapted to be folded together and adhesively united to form a closure for the carton, applying a layer of a heat-activable adhesive to a surface of a flap and then coating the blank with an air and moisture excluding layer of fusible material immiscible with the adhesive.

6. The method of closing and sealing a waxcoated carton having a flap adapted to be folded together with another flap to form a closure for the carton and provided with a layer of heat-activable adhesive immiscible with the wax and underlying the wax coating, which comprises interfolding the closure flaps, and subjecting them to heat and pressure whereby the wax overlying the adhesive is melted and squeezed from between the adhesive layer and the adjacent surface.

7. The method of forming a sealed container which comprises forming a container blank, applying a heat-activable adhesive to a seam surface of the blank, then applying an air and moisture excluding coating immiscible with the adhesive to the blank, forming the blank into the form of a container and sealing its seams under heat and pressure, whereby the coating overlying the adhesive is softened and flowed from the adhesive and an eifective adhesive bond is formed.

8. The method of forming a container which comprises forming a container blank having a seam area adapted to be adhesively joined to another seam area of the blank to form a seam, applying to the seam area a heat-activable adhesive, and then coating the blank and the adhesive with a coating of fusible air and moisture excluding material immiscible with the adhesive.

9. The method of making a container element which comprises forming a blankhaving an area adapted to be adhesively joined to another area of the blank in forming the blank into a container element, applying to the first said area a heatactivable adhesive and then coating the blank and adhesive with a fusible air and moisture-excluding material immiscible with the adhesive.

10. A blank for making container elements comprising a blank body having an area adapted to be united to another area of the body in forming the blank into a container element, a layer of a heat-activable adhesive on the surface of the body and within said first mentioned area, and a coating of fusible airand moisture-excluding material immiscible with the adhesive, covering the body and overlying the adhesive.

11. A container element comprising a first. portipn having its surface united to the surface of an adjacent portion of the element, a heat activable adhesive layer between said surfaces forming an adhesive bond joining said portions together, and an air and moisture-proof coating immiscible with the adhesive, covering the surface of the element and surrounding the adhesive layer.

' JACOB G. MARK.

FRANCIS W. LANIGAN. 

